Papers by Keyword: Selective Laser Sintering (SLS)

Abstract: The SLS (Selective Laser Sintering, SLS) technology can directly manufacturing any complex structure, however, due to the limitation of the manufacturing engineering factor, the surface quality and the dimension accuracy of the green part are still an outstanding problem. So, the experimental methods were adopted to study the effect of part orientation on the machining accuracy, the part orientation will significantly affects the outline of the part due to the stair-stepping phenomenon, and then affects the surface quality and the dimension accuracy. The experimental samples of different part orientations including 0, 20, 45, 60, 90 degree were fabricated, and the results indicated that the stair-stepping phenomenon significantly affected by the part orientation, when the part orientation is 0, 45 and 90 degree, the dimension accuracy is best than other part orientation, it mean the stair-stepping phenomenon is smallest. So, when the part structure is complicated, the important structure dimension should be chosen the orientation 0, 45, or 90 degree

Abstract: A three dimensional geometric model of a homemade selective laser sintering (SLS) system is simplified and imported into Ansys Finite Element Software for static and modal analysis. The analysis results show that the supporting base that holds up the laser system undergoes large deformations. The machining accuracy can hardly meet the high-precision requirements of sintered parts with complex internal and external geometries. A method is put forward for the structural optimization of the SLS system. The calculation results show that the bending deformation of the supporting base decreases by 73.2%, and the maximum stress also decreases significantly. It indicates that the high precision manufacturing can be achieved with the improved SLS system.

Abstract: The dimensional accuracy of shells and binders of investment casting which incorporation with selective laser sintering is investigated. The results show that the dimensional accuracy of colloidal silica is higher than that of ethyl silicate, and the dimensional variation rate of investment casting shells produced with colloidal silica is much lower than ethyl silicate shells. Moreover, colloidal silica possesses better performance on environmental protection and production cost control. These indicate that the comprehensive properties of colloidal silica are better than that of ethyl silicate. Meanwhile, the average dimensional variation rate of the single colloidal silica shell and the ethyl silicate-colloidal silica alteration shell was almost identical and it was much lower than that of the other shells which were produced in this study. This means two kinds of shells are optimized in all five types of shells studied in the aspect of dimensional accuracy. The unique properties of two shells show clearly direction to choose the type of shell.

Abstract: Directly driven by CAD model, based on principle of discrete-superposition, rapid prototyping technology is the generic terms of rapid manufacturing 3-dimensional physical entities with any complex shape. One of its main development trends is direct rapid manufacturing for metal parts. Up to now, there are many methods utilizing laser beam containing selective laser melting, selective laser sintering and laser engineered net shaping. Research and development of these means for direct rapid metal manufacturing are presented in this paper. Digital direct rapid manufacturing for metal parts represents development direction of advanced manufacturing technology.

Abstract: Sintering temperature influences on sintering process essentially. Laser power and scanning speed determined sintering temperature. Preheat to powder is beneficial to improve the surface temperature uniformity. Stress concentration of part is various in different layer depth. Therefore, the influence of laser power, scanning speed, thickness of spreading layer and preheat temperature on part quality in selective laser sintering(SLS) are main factors. Based on laser energy in Gaussian distribution and mechanism of SLS, with manufactured specimen pieces by molding machine AFS-450, orthogonal experimental design and analysis of variance are adopted to post-treatment. The prototyping sintering parameters are optimized. The result and solution of the experiment are the preheat temperature of 100°C, the scanning speed of 2000 mm/s, the laser power of 24W, the thickness of single layer of 0.2mm for ABS resin. This work can provide optimized parameters in SLS for ABS resin. It will be of benefit to improve the part dimensional precision and strength.

Abstract: This work compared the densification behavior and pores evolution of two kinds of samples (15% and 35% initial porosity stainless steels parts) prepared by selective laser sintering. The results show that post microwave sintering process results in an increase of the density of sample. At the low sintering temperature (1200°C, 1300°C), the low porosity can lead to high density in the final sintered sample. As the sintering temperature reaches 1400°C, however, the sample with 35% initial porosity could be sintered to the higher final density than that of the sample with 15% initial porosity. The results also indicate that the initial porosity has a great effect on the number of pores, pore size, pore shape and the distribution of pores during post sintering process.

Abstract: Binding additives used in selective laser sintering (SLS) of metal powders determine the vital performance of untreated metal prototypes. The types of polymer binding materials were presented in this work. The binding conditions and processes were represented. The thermal variations of binding additives and interfaces actions between polymer and metal were discussed. This work provides a reference for the selection of polymer binding additives in SLS.

Abstract: Selective laser sintering (SLS) is one of relatively mature rapid prototyping technologies at present day. This paper takes the forming of a high voltage switch casting model in the AFS-3000 rapid prototyping system as example to describe the forming process of SLS, and introduce the casting model rapid prototyping technology based on SLS. This research provides a powerful technological support for rapid development of casting products.

Abstract: In this paper the research focused on the viability of using the selective laser sintering (SLS) technique for creating tissue engineer (TE) scaffolds. A biocomposite blend comprising polylactic acid (PLA) and hydroxyapatite (HA) was used in the research to study the feasibility of the blend to develop scaffolds. The biocomposite blends obtained via physical blending were subjected to laser sintering to fabricate test specimens. The test specimens were characterized using scanning electron microscopy (SEM) and the components before sintering and after sintering were analyzed by infrared spectrophotometry (IR). The results obtained ascertained that SLS-fabricated scaffolds have good potential for TE applications

Abstract: This paper presents experimental investigations on influence of important process parameters viz., laser power, scan speed, layer thickness, hatching space along with their interactions on dimensional accuracy of Selective Laser Sintering (SLS) processed pro-coated sand mold. It is observed that dimensional error is dominant along length and width direction of built mold. Optimum parameters setting to minimize percentage change in length and width of standard test specimen have been found out using Taguchi’s parameter design. Optimum process conditions are obtained by analysis of variance (ANOVA) is used to understand the significance of process variables affecting dimension accuracy. Scan speed and hatching space are found to be most significant process variables influencing the dimension accuracy in length and width. And laser power and layer thickness are less influence on the dimension accuracy. The optimum processing parameters are attained in this paper: laser power 11 W; scan speed 1200 mm/s; layer thickness 0.5 mm and hatching space 0.25 mm. It has been shown that, on average, the dimensional accuracy under this processing parameters combination could be improved by approximately up to 25% compared to other processing parameters combinations.